Game concept
Supporter
The game also links it as Supporters.
From the game's encyclopedia
Supporters are Guests at the Coronation Activity supporting the Host in their ascension to the throne. They will have special opportunities to aid the Ruler in securing their Legitimacy.
They are directly opposed to the Detractors, guests who are attempting to foil the host.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Supporter is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Supporters are Guests at the Coronation Activity supporting the Host in their ascension to the throne." It is part of Coronation. The game also links it as Supporters. Patch 1.20.1.2, from game/common/game_concepts/ach_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/ach_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.